Distorted display on monitor, seeking possible cause.

The display on my monitor is distorted, i.e. it presents as a series of vertical lines along the width of the screen, but, as the same thing occurs when a different monitor is connected, I guess it is a PC problem.

I bought the package from Comet in November 2007 which includes HP M9065 + HP W2207H monitor + 5 year guarantee, which unfortunately means it wasn’t long out of guarantee when the problem started. Further, because Comet have now closed, they are unable to assist, provide advice, or supply names of their previous technical repair staff.

Could a faulty graphics card be the cause of the problem, or could there be other causes?

I would guess you bare correct that the problem is with the PC. The spec you give shows the possibility of an internal on-board graphics chip and an Nvidia card. Which is the case for your machine. If you have the Nvidia card installed then it could be that causing the problem. Can you remove it and switch to the on-board graphics. (usually need to select this in the BIOS and connect the cable to the onboard monitor socket).

Seems to be graphics card, make sure it is firmly seated and hasn't worked loose. If still same prob with display, remove the card and swap the connector on back of pc, plug it into the onboard graphics.

Sadly I am far from being technically competent, but if my computer does have both an internal on-board graphics chip and an Nvidia card, and the Nvidia card is removed, will the computer work without it, or would it have to be replaced?

I seem to remember the computer package I bought was marketed as being good for gaming, but I chose it because it enabled me to easily watch and save numerous TV craft programmes, as well as offering normal computing facilities, so maintaing a clear display is important.

If you remove the video card the onboard graphics should work but you will need to connect your monitor to the socket on the computer which is fed by the onboard graphics. Look and see if there is a similar socket on the back of your computer to the one that is connected on the video card. If so just connect the monitor to it and remove the video card.
To remove it switch off the computer and disconnect it from the mains electricity supply. Open up the computer and locate the video card.Remove the single screw which holds the piece of metal to the computer case. Remove the card by gently pulling it out. Depending on what type of card it is there may be a locking tab at the far end of the socket to which it is fitted. Do not touch any other part of the card except the metal part without touching a bare part of the metal case with both hands or damage to the card could result due to static electricity.
You may have to go into the BIOS to select onboard graphics. so before you do anything boot up the computer and on the start vup screens that flash through in black and white look for the instruction of how to enter the bios, it is usually to press F2 or Del whilst the screens are flashing through. Once in the bios do not change anything except the entry on one of the tabs that reads something like "Set Primary Display". Highlight it and press enter which usually give a menu of choices. Select onboard graphics and press enter.
Press Esc several times to get to the first screen and then right arrow key until a menu comes up with Save changes and exit. Select this and press enter. There will be a confirmation screen which you agree. The computer should then boot up. You may have to do this whilst the original card is still in so that there is a working display but if just switching the plug to the new socket works then fine.

AS above, have a look at the back of the Box for another monitor socket, do not remove plug while PC switched on. This should be done with it switched off, If it as onboard Graphics it may not need another card fitting. You will only find out by trying it. If its connected to Onboard Graphics it will work if card removed or left in place